private void button1_Click_1(object sender, EventArgs e)

        {

            string path = Application.StartupPath;

            using (FileStream file = new FileStream(txtpath.Text, FileMode.Open))

            {

                Image img = Image.FromStream(file);

                string format;

                System.Drawing.Imaging.ImageFormat _img_format = GetImageFormat(img, out format);

                if (_img_format != null)

                {

                    img.Save(path + @"\" + Guid.NewGuid().ToString() + format, _img_format);

                    MessageBox.Show("ok");

                }

            }

           

        }

 

        /// <summary>

        /// 获取Image图片格式

        /// </summary>

        /// <param name="file"></param>

        /// <param name="format"></param>

        /// <returns></returns>

        private System.Drawing.Imaging.ImageFormat GetImageFormat(FileStream file, out string format)

        {

            byte[] sb = new byte[2];  //这次读取的就是直接0-1的位置长度了.

            file.Read(sb, 0, sb.Length);

            //根据文件头判断

            string strFlag = sb[0].ToString() + sb[1].ToString();

            //察看格式类型

            switch (strFlag)

            {

                //JPG格式

                case"255216":

                    format = ".jpg";

                    return System.Drawing.Imaging.ImageFormat.Jpeg;

                //GIF格式

                case"7173":

                    format = ".gif";

                    return System.Drawing.Imaging.ImageFormat.Gif;

                //BMP格式

                case"6677":

                    format = ".bmp";

                    return System.Drawing.Imaging.ImageFormat.Bmp;

                //PNG格式

                case"13780":

                    format = ".png";

                    return System.Drawing.Imaging.ImageFormat.Png;

                //其他格式

                default:

                    format = string.Empty;

                    return null;

            }

        }

 

        /// <summary>

        /// 获取Image图片格式

        /// </summary>

        /// <param name="_img"></param>

        /// <param name="format"></param>

        /// <returns></returns>

        private System.Drawing.Imaging.ImageFormat GetImageFormat(Image _img,out string format)

        {

            if (_img.RawFormat.Equals(System.Drawing.Imaging.ImageFormat.Jpeg))

            {

                format = ".jpg";

                return System.Drawing.Imaging.ImageFormat.Jpeg;

            }

            if (_img.RawFormat.Equals(System.Drawing.Imaging.ImageFormat.Gif))

            {

                format = ".gif";

                return System.Drawing.Imaging.ImageFormat.Gif;

            }

            if (_img.RawFormat.Equals(System.Drawing.Imaging.ImageFormat.Png))

            {

                format = ".png";

                return System.Drawing.Imaging.ImageFormat.Png;

            }

            if (_img.RawFormat.Equals(System.Drawing.Imaging.ImageFormat.Bmp))

            {

                format = ".bmp";

                return System.Drawing.Imaging.ImageFormat.Bmp;

            }

            format = string.Empty;

            return null;

        }